A stability control method for the reconfiguration of metamorphic robots

Abstract

The present invention discloses a stability control method for the reconfiguration of a metamorphic robot, including: 1. Generating the desired trajectories of each joint during the reconfiguration of the metamorphic robot; 2. Inputting the deviations between the desired trajectories of the joints and the mass-centroid adjustment sliders and the actual trajectories into a sliding mode controller, calculating and outputting the actual required torques for the movement of each joint and the mass-centroid adjustment sliders during the reconfiguration process; 3. Inputting the actual required torques for the movement of each joint and the mass-centroid adjustment sliders during the reconfiguration process into a dynamic model to obtain the actual trajectories of each joint and the mass-centroid adjustment sliders; 4. Calculating the actual value of the ZMP of the metamorphic robot using the actual trajectories of the movement of each joint and the mass-centroid adjustment sliders, and feeding it back to the fuzzy PID control module to form an upper closed-loop control for stability. The present invention can make the actual ZMP position of the whole vehicle approach the theoretical reference position, thereby improving the stability during system reconfiguration.

Description

Technical Field

[0001] The present invention belongs to the technical field of robot stability control, and specifically relates to a stability control method for the reconfiguration process of a metamorphic robot. Background Art

[0002] Mobile robots are one of the research hotspots in the field of robotics currently. They mainly cover related disciplines such as mechanical structures, non-linear system dynamics, sensor technology, computer technology, motor control technology, and artificial intelligence, and are an important manifestation of a country's scientific and technological strength and development level. Currently, the most widely used mobile robots mainly include: wheel-driven vehicle types, walking robots, and crawler-driven robots. However, each of these three types of robots has its own advantages and disadvantages in terms of motion patterns. Among them, wheel-driven vehicle-type robots are the most common. They mainly rely on drive wheels similar to vehicles for movement, with fast movement speed but poor obstacle-crossing ability; walking robots use a walking and running movement method, which can adapt to complex terrains but have a complex structure and slow movement speed; crawler-driven robots have strong obstacle-crossing ability, but high energy consumption and poor endurance. Therefore, mobile robots with only a single motion pattern cannot simultaneously possess comprehensive performances such as fast movement on paved structural roads, obstacle-crossing walking on rugged mountains, and high endurance. In addition, most of the traditional stability control methods applied to various actions such as robot walking and reconfiguration mostly adopt motion adjustment strategies based on the movement of the robot's ankle or hip joints. Such methods simplify the robot into a three-dimensional inverted pendulum model, and the attitude control of the robot can be achieved by adjusting the angles of the ankle or hip joints, thereby improving the stability of the robot. However, since the robot is a multi-degree-of-freedom, strongly coupled variable-structure dynamic system, the modeling process of its control system is relatively complex, and during processes such as walking or reconfiguration, the ankle or hip joints of the robot also need to complete their own motion laws, and the stability control effect that can be provided is relatively limited. Summary of the Invention

[0003] The present invention aims to solve the above-mentioned deficiencies existing in the prior art and provides a stability control method for the reconfiguration of a metamorphic robot, in order to achieve the actual ZMP position of the whole vehicle approaching the theoretical reference position, thereby improving the stability during system reconfiguration.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The stability control method for the reconfiguration of a metamorphic robot according to the present invention is characterized in that the metamorphic robot includes: a front body, a rear body, folding legs, a lifting mechanism, a center-of-mass adjustment mechanism, and an upper-layer fuzzy PID controller and a lower-layer sliding mode controller for stability control; wherein, a pair of hub motors and a pair of MacPherson struts are arranged on the front body; the folding legs, the center-of-mass adjustment mechanism, and the lifting mechanism are arranged on the top plate of the rear body, and a pair of hub motors, a pair of MacPherson struts, and a braking device are also arranged below the rear body; the lifting mechanism performs rotational motion and translational motion through a lifting motor and an electric push rod respectively, and a center-of-mass adjustment slider that moves in the vertical and horizontal directions is arranged in the center-of-mass adjustment mechanism; the stability control method is carried out according to the following steps:

[0006] Step 1: Generate the desired trajectories of each joint during the reconfiguration of the metamorphic robot;

[0007] Step 1.1: Establish the kinematic model of the reconfiguration of the metamorphic robot;

[0008] Step 1.2: According to Lagrangian dynamics theory, use Equation (7) to establish the dynamic model of the reconfiguration of the metamorphic robot;

[0009] (7)

[0010] In Equation (7): is expressed as a set of generalized coordinates of the metamorphic robot, and , where, are the rotational angles of the ankle, knee, hip on the folding leg and the lifting joint of the lifting mechanism respectively, is the translational distance of the center-of-mass adjustment slider and the electric push rod; are respectively the first and second derivatives of; is the mass matrix term; is the Coriolis term; is the gravity term; are the driving torques of each joint of the metamorphic robot, where, is the driving torque of the ankle joint; is the driving torque of the knee joint; is the driving torque of the hip joint; is the driving torque of the center-of-mass adjustment slider; is the driving torque of the lifting joint; is the driving torque of the electric push rod;

[0011] Step 1.3: Use the fifth-order polynomial fitting method shown in Equation (8) to construct the desired trajectory of any ;

[0012] (8)

[0013] In Equation (8), represent the ankle joint, knee joint, hip joint, and lifting joint respectively, is the angle of rotation required for the th joint to complete the reconstruction, is the initial rotation angle of the th joint,

[0014] Step 1.4: Taking the center point of the foot support area of the metamorphic robot as the desired zero-moment point position, the deviation between the actual zero-moment point position of the metamorphic robot at time t and the desired zero-moment point position as well as the change rate of the deviation are input into the upper-layer fuzzy PID controller to calculate and output the desired trajectory of the mass-centroid slider at time t;

[0015] Step 2: Calculate the deviation between the actual trajectory of the th joint of the metamorphic robot at time t and the desired trajectory , and the deviation between the actual trajectory of the mass-centroid slider of the metamorphic robot and the desired trajectory ; where, ;

[0016] Step 3: Input the two deviations into the lower-layer sliding mode controller to calculate the torque required for the reconstruction process of each joint and the torque

[0017] required to adjust the movement of the mass-centroid slider of the metamorphic robot; ;

[0018] (9)

[0019] In Equation (9), represents a diagonal constant coefficient matrix, is the tracking error, and , is the derivative of;

[0020] Step 3.2: Construct the reaching law with an exponential reaching law using Equation (10) :

[0021] (10)

[0022] In Equation (10), and represent two diagonal constant coefficient matrices, and , represents the diagonal constant coefficient matrix the i-th diagonal coefficient in, and 0; , represents the diagonal constant coefficient matrix the i-th diagonal coefficient in, and 0; represents the sign function, where ;

[0023] Step 3.2: Differentiate Equation (9) and substitute the dynamic model into Equation (9), so as to obtain the output torque of the sliding mode controller by using Equation (11) ;

[0024] (11)

[0025] In Equation (11), represents the desired trajectory of the -th joint of the metamorphic robot and the mass-centroid slider at time t;

[0026] Step 4: Substitute and into Equation (7) to obtain the actual trajectory of each joint and the actual trajectory of the mass-centroid slider ;

[0027] Step 5: Substitute and into the centroid calculation formula of various components of the metamorphic robot to obtain the centroid positions of various components , where respectively represent 6 components, successively including: the calf, thigh, rear body, lower lifting rod, front body, and electric push rod of the metamorphic robot; thus, the actual zero-moment point position of the metamorphic robot at time t is obtained by using Equation (12) and input it into the fuzzy PID controller to achieve the upper-layer closed-loop control of the stability of the metamorphic robot;

[0028] (12)

[0029] In Equation (12), is the mass of each component of the metamorphic robot, , are respectively the coordinate values of the centroid of the th component in the , axis directions of the coordinate axes, , are respectively the accelerations of the centroid of the component in the , axis directions of the coordinate axes, and is the gravitational acceleration.

[0030] An electronic device according to the present invention includes a memory and a processor, characterized in that the memory is used to store a program for supporting the processor to execute the stability control method, and the processor is configured to execute the program stored in the memory.

[0031] A computer-readable storage medium according to the present invention, characterized in that when the computer program stored on the computer-readable storage medium is run by a processor, it executes the steps of the stability control method.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. In order to avoid impacts in the joint movement during the reconfiguration of the metamorphic robot, the present invention pre-sets the joint angle values at the starting and ending moments of the robot, and designs the joint angles of the metamorphic robot during reconfiguration as a function of time t based on quintic polynomial planning. By obtaining the robot joint motion sequence and applying it to the robot body, the smoothness of the joint movement during robot reconfiguration is achieved.

[0034] 2. The present invention takes the centroid adjustment mechanism installed on the body of the metamorphic robot as the control object, and realizes the stability of system reconfiguration by adopting a hierarchical control method. Among them, the upper-layer fuzzy PID controller serves as the position controller of the slider in the centroid adjustment mechanism. This controller mainly changes the position of the slider in the adjustment mechanism in real time according to the deviation between the actual ZMP and the ideal ZMP, so that it satisfies that the ZMP point is always near the center of the support area. The lower-layer sliding mode controller is used for the tracking control of each joint and the centroid adjustment slider to the desired trajectory, and finally realizes the closed-loop feedback control of the overall system.

[0035] 3. By the method of the present invention, when the metamorphic robot needs to further perform walking, turning and climbing, at this time, only the leg joints need to complete the walking, turning and climbing actions, and the stability of the system can also be controlled by the centroid adjustment mechanism. Since the two functions are respectively completed by two actuators, this can not only improve the stability of the robot during walking, turning and climbing, but also improve the rapid flexibility of the robot during walking, turning and climbing. Description of the Drawings

[0036] Figure 1 Schematic diagram of the structure and link model of the metamorphic robot involved in the present invention;

[0037] Figure 2 Schematic diagram of the mechanism degrees of freedom of the metamorphic robot involved in the present invention;

[0038] Figure 3 Schematic diagram of the structure and installation of the mass-centroid adjustment mechanism of the metamorphic robot involved in the present invention;

[0039] Figure 4 Schematic diagram of the reconstruction stability control principle of the metamorphic robot based on the dynamic mass-centroid adjustment mechanism of the present invention;

[0040] Figure 5a Simulation curve of the ZMP point of the system in the X direction before and after the reconstruction stability control of the metamorphic robot involved in the present invention without acceleration;

[0041] Figure 5b For the metamorphic robot involved in the present invention with an acceleration of Simulation curve of the ZMP point of the system in the X direction before and after the reconstruction stability control;

[0042] Figure 5c For the metamorphic robot involved in the present invention with an acceleration of Simulation curve of the ZMP point of the system in the X direction before and after the reconstruction stability control;

[0043] Reference numerals in the figure: 1, front body; 2, rear body; 3, folding leg; 4, lifting mechanism; 5, mass-centroid adjustment mechanism; 51, storage battery; 52, battery box; 53, drive motor. Detailed implementation manners

[0044] The following further describes the present invention in conjunction with the accompanying drawings and specific embodiments:

[0045] The metamorphic robot involved in the present invention is a multi-degree-of-freedom, multi-variable, non-linear, and complex dynamic system. As Figure 1 shown is the structure and link schematic diagram of the metamorphic robot involved in the present invention. The robot mainly includes a front body, a rear body, folding legs, a lifting mechanism, a mass-centroid adjustment mechanism, and an upper-layer fuzzy PID controller and a lower-layer sliding mode controller for stability control. Among them, a pair of hub motors and a pair of MacPherson struts are arranged on the front body; folding legs, a mass-centroid adjustment mechanism, and a lifting mechanism are arranged on the top plate of the rear body, and a pair of hub motors, a braking device, and a pair of MacPherson struts are also arranged below the rear body. The schematic diagram of the joint degrees of freedom of the metamorphic robot abstracted by a link mechanism is as Figure 2As shown, it includes three degrees of freedom at the hip joint, which is mainly responsible for the yaw, roll, and pitch movements of the entire leg. There is one degree of freedom at the knee joint, which is mainly responsible for the pitch movement of the calf. There are two degrees of freedom at the ankle joint, which are mainly responsible for the pitch and roll movements of the foot. The lifting mechanism includes a lifting motor, a V-shaped lifting rod, and an electric push rod, which perform rotational and translational movements through the lifting motor and the lifting push rod respectively. In the center-of-mass adjustment mechanism, there is a center-of-mass adjustment slider that moves in the vertical and horizontal directions.

[0046] The specific structure and layout of the center-of-mass adjustment mechanism are as Figure 3 shown. The main working principle of the center-of-mass adjustment mechanism is to use a motor to drive the center-of-mass adjustment slider to move quickly on the transverse and longitudinal tracks, and control the stability of the system reconstruction by changing the position of the center of mass (i.e., changing the ZMP position of the system). Among them, in order to make reasonable use of the mass of the battery, the battery is used as the center-of-mass adjustment slider in the center-of-mass adjustment mechanism.

[0047] In this embodiment, a method for controlling the stability of the reconfiguration process of a variable-cell robot based on a dynamic center-of-mass adjustment mechanism is as Figure 4 shown. This method uses a hierarchical controller, where the upper layer is a fuzzy PID controller and the lower layer is a sliding mode controller. The upper layer controller is used to solve the desired trajectory when the center-of-mass adjustment slider moves, and the lower layer controller calculates the torque required when the center-of-mass adjustment slider moves, so as to make the actual zero-moment point position of the variable-cell vehicle approach the desired zero-moment point position. Specifically, it includes the following steps:

[0048] Step 1: Generate the desired trajectories of each joint during the reconfiguration process of the variable-cell robot;

[0049] Step 1.1: Establish the kinematic model of the reconfiguration movement of the variable-cell robot;

[0050] Since the structure of the variable-cell robot has left-right symmetry, and its morphological changes and movements mainly occur in the front-back and up-down directions during the reconfiguration process, it is only necessary to perform a motion analysis of the mechanism in the vertical plane. As Figure 1 shown, a basic coordinate system is established at the exact center of the robot's supporting foot , and the x-axis points in the driving direction of the robot, the y-axis is perpendicular and points upward from the robot, and the direction of the z-axis is determined according to the right-hand rule of the coordinate system. Assume that the ankle joint angle in the leg mechanism of the variable-cell robot is , the knee joint angle is , the hip joint angle is , the angle between the equivalent rod of the rear body and the lower rod of the V-shaped lifting rod is , the lifting joint angle of the lifting mechanism is , and the angle between the electric push rod and the equivalent rod of the front body is , where the equivalent rod of the front body is the line connecting the hinge points of the V-shaped lifting rod and the front body and the hinge points of the electric push rod and the front body, and the equivalent rod of the rear body is the line connecting the hip joint and the lifting joint; 、 、 、 、 are the foot, calf, thigh, lower rod length of the V-shaped lifting rod, and the length of the equivalent rod of the front body of the metamorphic robot respectively, is the distance between the hip joint and the lifting joint.

[0051] Simplify the mass centers of the components of the metamorphic robot to the geometric centers of the components, that is, the midpoints of the rods. According to the link relationship, the coordinates of the mass centers of the main components of the metamorphic robot in the base coordinate system can be obtained , where respectively represent the calf, thigh, rear body, V-shaped lifting rod, front body, and electric push rod components of the metamorphic robot.

[0052] Among them: The coordinates of the mass center of the calf in the base coordinate system:

[0053] (1)

[0054] In the formula: ; ;

[0055] The coordinates of the mass center of the thigh in the base coordinate system:

[0056] (2)

[0057] In the formula: ; ;

[0058] The coordinates of the mass center of the rear body in the base coordinate system:

[0059] (3)

[0060] In the formula: ; ;

[0061] The coordinates of the mass center of the V-shaped lifting rod in the base coordinate system:

[0062] (4)

[0063] In the formula: ; ;

[0064] The coordinates of the mass center of the front body in the base coordinate system:

[0065] (5)

[0066] In the formula: ; ;

[0067] The coordinates of the center of mass of the electric push rod in the base coordinate system:

[0068] (6)

[0069] In the formula: ; ;

[0070] Step 1.2: According to the Lagrangian dynamics theory, use Equation (7) to establish the dynamic model of the metamorphic robot reconstruction;

[0071] (7)

[0072] In Equation (7): Represents a set of generalized coordinates of the metamorphic robot, and , where Are the rotational angles of the ankle, knee, hip of the folding leg and the lifting joint of the lifting mechanism respectively, Is the translational distance of the conditioning center of mass slider and the electric push rod; Are respectively The first and second derivatives of; Is the mass matrix term; Is the Coriolis term; Is the gravity term; Are the driving torques of each joint of the metamorphic robot, where Is the driving torque of the ankle joint; Is the driving torque of the knee joint; Is the driving torque of the hip joint; Is the driving torque of the conditioning center of mass slider; Is the driving torque of the lifting joint; Is the driving torque of the electric push rod;

[0073] Step 1.3: Use the fifth-order polynomial fitting method shown in Equation (8) to construct the expected trajectory Of any ;

[0074] (8)

[0075] In Equation (8), Respectively represent the ankle joint, knee joint, hip joint and lifting joint, Is the The angle that a joint needs to rotate to complete reconstruction is the initial rotation angle of the th joint;

[0076] Step 1.4: Take the center point of the foot support area of the metamorphic robot as the desired zero-moment point position, and use the actual zero-moment point position of the metamorphic robot at time t and the desired zero-moment point position deviation and the change rate of the deviation are input into the upper-layer fuzzy PID controller to calculate and output the desired trajectory of the mass-centering slider at time t ;

[0077] Take the center point of the foot support area of the metamorphic robot (i.e., the desired ZMP position ) and deviation and the change rate of the deviation as the input of the fuzzy controller, and the output is , , . First, perform fuzzy processing on and and input the processed data into the fuzzy controller; after fuzzy processing, fuzzy inference, and defuzzification, obtain , , , and then obtain the new PID control parameter values.

[0078] Step 1.4.1: Determine the fuzzy universe of discourse: The universe of discourse of the deviation is ; The universe of discourse of the deviation change rate is ; The universe of discourse of is ; The universe of discourse of is ; The universe of discourse of is .

[0079] Step 1.4.2: Determine the fuzzy sets: The fuzzy control input and output fuzzy sets are , representing respectively ,

[0080] Step 1.4.3: Determine the membership function: Triangular membership function.

[0081] Step 1.4.4: Establish fuzzy rules;

[0082] , , The fuzzy rules are shown in Tables 1 - 3.

[0083] Table 1 Fuzzy rules

[0084]

[0085] Table 2 Fuzzy rules

[0086]

[0087] Table 3 Fuzzy rules

[0088]

[0089] Step 2: Calculate the actual trajectory of the th joint of the metamorphic robot at time t and its deviation from the desired trajectory , and calculate the actual trajectory of the mass - centering slider and its deviation from the desired trajectory ; where ;

[0090] Step 3: Input the two deviations into the lower - layer sliding - mode controller to calculate the torque required for the reconstruction process of each joint and the torque required to adjust the movement of the mass - centering slider of the metamorphic robot ;

[0091] Step 3.1: Construct the switching - surface function using Equation (9) ;

[0092] (9)

[0093] In Equation (9), represents a diagonal constant - coefficient matrix, is the tracking error, and , is the derivative of ;

[0094] Step 3.2: Construct the reaching law with an exponential reaching law using Equation (10) :

[0095] (10)

[0096] In Equation (10), and represent two diagonal constant - coefficient matrices, and , represents the i-th diagonal coefficient in the diagonal constant coefficient matrix , and 0; , represents the i-th diagonal coefficient in the diagonal constant coefficient matrix , and 0; represents the sign function, where ;

[0097] Step 3.2: Take the derivative of Equation (9), and substitute the dynamic model into Equation (9), so as to obtain the output torque of the sliding mode controller by using Equation (11) ;

[0098] (11)

[0099] In Equation (11), represents the -th joint and the expected trajectory of the conditioned center-of-mass slider;

[0100] Step 4: Substitute and into Equation (7) to obtain the actual trajectories of each joint and the actual trajectory of the conditioned center-of-mass slider ;

[0101] Step 5: Substitute and into the centroid calculation formula of each component of the metamorphic robot to obtain the centroid positions of each component , where respectively represent the calf, thigh, rear body centroid, lower rod centroid of the lifting rod, front body centroid, and each component of the electric push rod of the metamorphic robot; thus, the actual zero-moment point position of the metamorphic robot at time t is obtained by using Equation (12) , and input it into the fuzzy PID controller to achieve the upper-layer closed-loop control of the stability of the metamorphic robot;

[0102] (12)

[0103] In Equation (12), is the mass of each component of the metamorphic robot, , are respectively the centroid of component in the , coordinate axis directions, , are respectively the centroid of component in the , The acceleration in the coordinate axis direction is the gravitational acceleration.

[0104] In this embodiment, an electronic device includes a memory and a processor. The memory is used to store a program that supports the processor to execute the above method, and the processor is configured to execute the program stored in the memory.

[0105] In this embodiment, a computer-readable storage medium stores a computer program on the computer-readable storage medium. When the computer program is run by a processor, it executes the steps of the above method.

[0106] The change curve of the ZMP point in the X direction of the system before and after reconstructing the stability control of the mass centering mechanism is as Figure 5a shown. As Figure 5a can be seen, without control, the ZMP point is close to the edge of the support area at the beginning and end of the reconstruction process, indicating that the metamorphic robot is close to the unstable state. To ensure the stability of the reconstruction, in the reconstruction stability control strategy of the metamorphic robot, two control strategies, namely fuzzy PID control and PID control, are respectively adopted for the mass centering mechanism. As Figure 5a shown by the ZMP curves of the metamorphic robot under PID control and fuzzy PID control, the stability control can make the ZMP curve stable near the center of the support area.

[0107] During the driving reconstruction process, the metamorphic robot will be affected by acceleration, which will change the position of the ZMP point, and there is a possibility that the ZMP exceeds the support area and the metamorphic robot topples and becomes unstable. As Figure 5b 、 Figure 5c shown are the ZMP curves of the metamorphic robot during the reconstruction process when the driving acceleration is 、 . When the acceleration is , if there is no mass centering mechanism for stability control during the reconstruction process, the ZMP exceeds the support area at the end of the reconstruction. When the acceleration received by the metamorphic robot during the reconstruction process increases to , the time when it exceeds the support area advances, and it is more likely to topple and become unstable. When there is acceleration during the reconstruction process, performing stability control on the metamorphic robot can also ensure that the ZMP is maintained near the support area. Compared with PID control, the ZMP point can reach the center of the support area faster under fuzzy PID control, and the ZMP curve under fuzzy PID control during the reconstruction process fluctuates less, having a better stability control effect.

Claims

1. A stability control method for the reconfiguration of metamorphic robots, characterized in that, The metamorphic robot includes: a front body, a rear body, folding legs, a lifting mechanism, a center-of-mass adjustment mechanism, and an upper-layer fuzzy PID controller and a lower-layer sliding mode controller for stability control; among them, a pair of hub motors and a pair of MacPherson struts are arranged on the front body; the folding legs, the center-of-mass adjustment mechanism, and the lifting mechanism are arranged on the top plate of the rear body, and a pair of hub motors, a pair of MacPherson struts, and a braking device are also arranged below the rear body; the lifting mechanism performs rotational motion and translational motion through a lifting motor and an electric push rod respectively, and a center-of-mass adjustment slider that moves in the vertical and horizontal directions is arranged in the center-of-mass adjustment mechanism; the stability control method is carried out according to the following steps: Step 1: Generate the desired trajectories of each joint during the reconstruction process of the metamorphic robot; Step 1.1: Establish the kinematic model of the reconstruction of the metamorphic robot; Step 1.2: According to the Lagrangian dynamics theory, establish the dynamic model of the reconstruction of the metamorphic robot using Equation (7); (7) In formula (7): represents a set of generalized coordinates of the metamorphic robot, and , where are respectively the rotation angles of the ankle, knee, hip on the folding leg and the lifting joint of the lifting mechanism, is the translational distance of the mass-centroid adjustment slider and the electric push rod; are respectively the first and second derivatives; is the mass matrix term; is the Coriolis term; is the gravity term; is the driving torque of each joint of the metamorphic robot, where is the driving torque of the ankle joint; is the driving torque of the knee joint; is the driving torque of the hip joint; is the driving torque of the mass-centroid adjustment slider; is the driving torque of the lifting joint; is the driving torque of the electric push rod; Step 1.3: Use the fifth-order polynomial fitting method shown in Equation (8) to construct the desired trajectory of any th joint among the ankle joint, knee joint, hip joint, and lifting joint of the metamorphic robot at time t ; (8) In Equation (8), respectively represent the ankle joint, knee joint, hip joint, and lifting joint, is the angle of rotation required for the -th joint to complete the reconstruction, is the initial rotation angle of the -th joint; Step 1.4: Taking the center point of the foot support area of the metamorphic robot as the desired zero-moment point position, the actual zero-moment point position of the metamorphic robot at time t and the desired zero-moment point position deviation and the change rate of the deviation are input into the upper-layer fuzzy PID controller to calculate and output the desired trajectory of the center-of-mass slider at time t ; Step 2: Calculate the actual trajectory of the metamorphic robot at the th joint at time t and the deviation from the desired trajectory ; and the actual trajectory of the mass-centroid slider and the deviation from the desired trajectory ; where ; ; ; Step 3: Input the deviation and the deviation into the lower layer sliding mode controller for calculating the torque required for the reconstruction process of each joint and the torque required for adjusting the movement of the centroid slider of the metamorphic robot ; Step 3.1: Construct the switching surface function using Equation (9) ; (9) In Equation (9), represents a diagonal constant coefficient matrix, is the tracking error, and , is the derivative of; Step 3.2: Construct an exponential reaching law with the reaching rate using Equation (10) :[[]]END]] (10) In formula (10), and represent two diagonal constant coefficient matrices, and , represents the i-th diagonal coefficient in the diagonal constant coefficient matrix , and 0; , represents the i-th diagonal coefficient in the diagonal constant coefficient matrix , and 0; represents the sign function, where ; Step 3.3: Differentiate Equation (9), and substitute the kinetic model into Equation (9), so as to obtain the output torque of the sliding mode controller by using Equation (11). ; (11) In formula (11), represents the second derivative of the desired trajectory of the th joint of the metamorphic robot and the mass-centroid slider at time t; Step 4: Substitute and into Equation (7) to obtain the actual trajectories of each joint and the actual trajectory of the center-of-mass slider ; Step 5: Substitute and into the centroid calculation formulas of various components in the metamorphic robot to obtain the centroid positions of various components , where respectively represent 6 components, successively including: the calf, thigh, rear body, lower lifting rod, front body, and electric push rod of the metamorphic robot; thus, the actual zero moment point position of the metamorphic robot at time t is obtained by using Equation (12), and is input into the fuzzy PID controller to achieve the upper-layer closed-loop control of the stability of the metamorphic robot; (12) In Equation (12), is the mass of each component of the metamorphic robot, , are respectively the coordinate values of the centroid of the -th component in the , axis directions, , are respectively the accelerations of the centroid of component in the , axis directions, is the acceleration due to gravity.

2. An electronic device, comprising a memory and a processor, characterized in that, The memory is used to store a program that supports the processor to execute the stability control method described in Claim 1, and the processor is configured to execute the program stored in the memory.

3. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is run by the processor, it executes the steps of the stability control method described in Claim 1.

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